Power supply rejection ratio (PSRR) is an important characteristic for any amplifier. PSRR defines an ability of an amplifier to reject AC-ripple voltage on a supply voltage. PSRR can be expressed as a ratio of amplifier output ripple to power supply AC-ripple. The PSRR of an amplifier is dominated by the degree of resistor mismatch in the feedback resistors and input resistors when input common mode voltage is different from output common mode voltage. Reducing the resistor mismatch can improve PSRR, and thus improve the output quality of the amplifier. One conventional solution is to increase the size of the resistors. However, increasing the size of the resistors increases the circuit size of the amplifier, which is undesirable particularly in amplifiers for mobile devices. Furthermore, conventional manufacturing processes limit the resistor matching to approximately 70 dB under best circumstances. Thus, these conventional solutions are limited in their ability to improve PSRR.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for amplifiers employed in consumer-level devices, such as mobile phones. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art. Furthermore, embodiments described herein may present other benefits than, and be used in other applications than, those of the shortcomings described above.